Potential Use of Environmental Biological Samples for Retrospective Electron Paramagnetic Resonance Dosimetry of Radiation Accidents

Abstract

Retrospective dosimetry is one of the most important tools of accident dosimetry for environmental dose estimation when large-scale radiological incidents and nuclear mass-casualty events occur. Electron paramagnetic resonance (EPR) dosimetry is a physical method for the retrospective assessment of absorbed dose based on the measurement of stable radiation-induced radicals in materials. Different from the fast disappearance of radials in aqueous systems, the radials can persist indefinitely in some organized matrices. Therefore, environmental materials contained in creatures from sea or land can be potentially used as environmental dosimeters for a retrospective dose analysis. This study aims to assess the EPR signals of free radicals from environmental biological samples, potentially for the retrospective dose estimation. The evaluated samples involve ox bone, cyclina shell, clam shell, chitin from squid, and human tissue (enamel and fingernail). First, we dehydrate and grind these materials to the powder with different sizes. Subsequently, all materials were irradiated with different doses ranging from 5 Gy to 50 Gy using 6 MV linear accelerator, and EPR spectra of these materials were obtained from the calculation of peak-to-peak amplitudes. The dose-response curve of EPR signals versus irradiated dose for the six materials shows good linearity (R2~0.99). For the grain-size experiment, the ox bone and tooth with 0.5 mm, the chitin with 0.1 mm, and the others with 1 mm have the strongest signal. For the storage temperature experiment, the optimal temperature of storage is at −20 °C for tooth, fingernail, ox bone, and chitin, at 45 °C for clam shell and cyclina shell where the signal fading is minimal. In conclusion, the developed dose-response curves of the six materials may potentially help a fast, rough retrospective dose reconstruction under the environment when radiation accidents occur.

L-Band Electron Paramagnetic Resonance Tooth Dosimetry Applied to Affected Cattle Teeth in Fukushima

“…Electron paramagnetic resonance (EPR) tooth dosimetry is an established method for evaluating the absorbed dose ionizing radiation by measuring the unpaired electrons to in-teeth samples [1]. In some studies, EPR dating measurements are also carried out using the radiation-induced EPR signals from background radiation in the environment where the samples were located [2]. Most EPR measurements are performed in the X-band and some aim to detect signals in small amount of samples with the higher-frequency Q-band measurements [3].…”